While the present invention relates to both diesel engines and Otto cycle (gasoline) engines, the apparatus that was initially developed was designed specifically for diesel engines.
Internal combustion engines of a diesel type are characterized by their injection of a carefully premeasured charge of liquid fuel directly into the compression-heated air of a combustion chamber formed by the rapid, inward movement of a piston in its cylinder. This is no premixing of fuel and air prior to injection.
This heterogeneous mixture of fuel and air at the time of injection which occurs when the piston is near top-dead-center of its compression stroke, has created challenges for diesel engineers since the invention of the engine by Rudolf Diesel in the 1890's. These include the accurate control of beginning and ending of injection, the rate at which the fuel is injected, the shape and direction of the injection spray, and the formation and control of the hydraulic pressure under which the fuel is forced into the engine cylinder. A diesel fuel system, in addition to providing the correct volume of fuel charge at each injection for all speed and load conditions, must also control fuel delivery for cold starting of the engine, govern idle and maximum speeds, and have fail-safe features to prevent engine "runaway" from occurring. In summary, the fuel injection system has for nearly a century been considered to be the heart of a diesel engine.
Both the technical and patent literature is replete with means suggesting solutions to above mentioned fuel injection related problems inherent in diesel engines. Various practical solutions have come about through the years as new technologies emerge in materials, manufacturing techniques, fuel chemistry and production processes. In recent times the newest technological contributions are in the areas of electronics and microprocessors whereby it now becomes feasible to control functions of engine operation heretofore considered impossible.
A study of prior art and published literature provides a well documented record of the progress in diesel fuel injection systems. One reference in this area is Burman and DeLuca, Fuel Injection and Controls for Internal Combustion Engines; 1962, which contains an historical section listing fuel injection developments as described mostly by patent literature. It is by no means complete, yet its offering is broad enough to show the devious and myriad attempts to solve the problems known to those skilled in the art.
Other relevant technical references include the following papers:
1. K. Komiyama, Electronically Controlled High Pressure Injection System for Heavy Duty Diesel Engine KOMPICS, Soc. of Auto. Engrs. Paper No. 810997, 1981. PA0 2. J. Akagi, A New Accumulator Fuel Injection System for Direct Injection Diesel Engines, Soc. of Auto. Engrs. Paper No. 821114, 1982. PA0 3. Ralph J. Hooker, "Orion--A Gas Generator Turbocompound Engine", Transactions, Soc. of Auto. Engrs., Vol. 65, 1957, pps 15-17.
The above references offer background falling within the scope of this patent, namely accumulator-type injectors with pressure multipliers. A worthwhile summary of commercially available diesel fuel systems may be found in Robert Brady, Diesel Fuel Systems, Reston, 1981.
From the earliest days of diesel engines, troubles were encountered with the fuel lines between the injection pump and nozzles. The unit injector combines the pump and nozzle, eliminates the high pressure lines, and thus offers a solution to the problem.
Many diesel engines are manufactured having a single cylinder, and the required fuel supply system is then relatively simple. Nevertheless, in addition to the injector associated with the one cylinder, the entire fuel supply system includes numerous additional components. For multi-cylinder diesel engines the complete fuel supply system becomes relatively complex.
Fuel injectors are generally by far the most expensive component parts of a diesel engine. The reason is that they carry fuel pressures of many thousands of pounds per square inch, their mechanical operation occurs very rapidly, and in order to control both the quantity of the fuel charge and the timing of its injection with a desired level of precision, the mechanical parts of the injector mechanism itself must be manufactured with extremely precise tolerances.
In the diesel fuel injection systems currently in commercial use, the controls for the system are essentially mechanical in nature. Many different mechanical arrangements have been used for controlling the fuel supply to the engine in order to satisfy the engine speed and load conditions.
Pertinent prior art United States patents include the following:
Eichelberg, U.S. Pat. No. 2,283,725, 1942;
Falberg, U.S. Pat. No. 2,985,378, 1961;
Links, U.S. Pat. No. 3,835,829, 1974;
Luscomb, U.S. Pat. No. 4,219,154, 1980.
Eichelberg is an early example disclosing the use of an accumulator type injector in a fuel injection system.
The Falberg patent is entitled "Accumulator Type Injection Apparatus". It discloses a piston type metering pump that is contained in the same housing with a hydraulic accumulator and an injection valve. The fuel pump includes a pump chamber 12 which delivers a fuel charge on each stroke of the pump, the quantity of the fuel charge being adjustable by mechanical rotation of the pump plunger. A housing 20 provides an accumulator chamber 21. Within the accumulator chamber a one-way check valve 24 controls the admission of the fuel charge from the pump chamber 12 into the accumulator chamber 21. At the lower end of the accumulator, an outlet 29 communicates with the spray tip 22 which is provided with the usual injection orifices 23. An injection valve 28 (or needle valve member) is normally in contact with a valve seat 30 so as to close off the accumulator outlet 29. Transfer of a fuel charge from pump chamber 12 through the check valve 224 into the accumulator chamber 21 raises the internal pressure in the accumulator. When the pump stroke ends by opening a spill port, differential pressure acting on the needle valve member causes the injector to fire, delivering the fuel in a dispersed configuration through orifices 23 of the spray tip 22.
The Links U.S. Pat. No. 3,835,829 shows a fuel pump which operates intermittently, with time spaced injection strokes that provides a series of injection pulses of the fuel. During the timer interval between successive injection strokes, the work chamber of the pump is charged with pressurized fuel through a supply valve, so that the charging period of the pump is substantially longer than the injection period. The supply valve shown in this reference is a three-way solenoid valve.
The Luscomb U.S. Pat. No. 4,219,154 shows a fuel injection system which is electronically controlled by means of a solenoid valve. Fuel supplied through the valve is fed to a hydraulic intensifier having large and small cylinders with the smaller cylinder 66 being movable within a fuel metering chamber 50. The pressure of the fuel in chamber 50 is amplified to several times the supply pressure as it is introduced into a fuel injector 78 for discharge into the combuation chamber. The injection event proceeds essentially concurrently with the retracting motion of the intensifier pistons.
The present invention relates to Otto cycle (gasoline) engines as well as to diesel engines.